KR20160006632A - Optical sheet and edge light type backlight unit - Google Patents

Abstract

The present invention is to provide an optical sheet which can prevent the sticking with other members arranged and installed in a rear side, and also, can prevent damage to the optical sheet and/or other members. The optical sheet of the present invention comprises a transparent base sheet, and a sticking prevention unit arranged and installed in the rear side of the base sheet, and has a plurality of printed dots as the sticking prevention unit. The mean diameter of the printed dots is preferably no less than 1 μm and no greater than 200 μm. The ratio of the mean height to the mean diameter of the printed dots is preferably no less than 1/100 and no greater than 1. The printed dots are preferable to have a flat type hemisphere shape in which the height direction is shorter than the diameter direction. The existence density of the printed dots in the rear side of the base sheet is preferably 10 to 2,500 dots/mm^2. Main components of the printed dots are preferably an acrylic, urethane, or acrylic urethane based resin.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an optical sheet and an edge light type backlight unit (OPTICAL SHEET AND EDGE LIGHT TYPE BACKLIGHT UNIT)

The present invention relates to an optical sheet and an edge light type backlight unit.

BACKGROUND ART [0002] As a transmissive liquid crystal display device, a backlight system in which a liquid crystal layer is illuminated from the back side is popular, and a backlight unit such as an edge light type (sidelight type) or a direct lower type is provided on the back side of the liquid crystal layer. The edge light type backlight unit 41 generally includes a light source 42 and a rectangular plate-like light guide plate (not shown) disposed so as to follow the end of the light source 42 43 and a plurality of optical sheets 44 which are arranged in a superimposed manner on the surface side of the light guide plate 43. LEDs (light emitting diodes), cold cathode tubes, and the like are used as the light source 42, but LEDs are now widely used in view of miniaturization and energy saving. The optical sheet 44 includes (1) a light diffusion sheet 45 which is arranged on the front surface side of the light guide plate 43 and mainly has a light diffusion function, (2) a light diffusion sheet 45 arranged on the surface side of the light diffusion sheet 45 And a prism sheet 46 having a function of refracting toward the normal direction side are used.

The light-diffusing sheet 45 is used for almost uniformly dispersing the transmitted light beams, and for the purpose of uniformizing the brightness due to the light diffusing property and increasing the brightness in the frontal direction. 6B, the light diffusing sheet 45 includes a substrate layer 47 made of a synthetic resin, a light diffusion layer 48 laminated on the surface of the base layer 47, And an anti-sticking layer 49 laminated on the back surface of the layer 47. The anti-sticking layer 49 prevents sticking (adhesion) of the back surface of the light diffusing sheet 45 to the surface of the light guide plate 43, thereby causing interference fringes. The anti-sticking layer 49 generally has a spherical bead 50 and a binder 51 made of a thermosetting resin that covers the bead 50, Sticking with the light guide plate 43 is prevented by the projecting convex portion.

As the bead 50, acrylic beads are generally used (see Japanese Patent Application Laid-Open No. 2011-126274). However, since the acrylic beads are relatively hard, the surface of the light guide plate 43, which is laminated on the back surface of the light diffusion sheet 45, may be scratched off by the beads 50 protruding from the back surface of the binder 51 . When the light diffusing sheet 45 is processed into a shape conforming to the design of the backlight unit 41, the bead 50 is removed and the bead 50 is removed between the light diffusion sheet 45 and the light guide plate 43 The back surface of the light diffusion sheet 45 and / or the surface of the light guide plate 43 may be damaged. When the concave portion is formed on the surface of the light guide plate 43, the bead 50 is inserted into the concave portion and the bead 50 is brought into contact with the concave portion, The surface may be damaged. If a scratch occurs on the surface of the light guide plate 43 as described above, there arises a problem that luminance unevenness is caused by the scratch.

Japanese Patent Laid-Open No. 2011-126274

(Summary of the Invention)

(Problems to be Solved by the Invention)

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is an object of the present invention to provide an optical sheet capable of preventing scratching of an optical sheet and / or other members while preventing sticking to other members arranged on the back side, An object of the present invention is to provide an edge light type backlight unit.

An optical sheet according to the present invention is provided to solve the above problems. The optical sheet includes a transparent base sheet and a sticking prevention part arranged on the back surface of the base sheet. The sticking prevention part includes a plurality of printing dots .

The optical sheet is provided with anti-sticking portions on the back surface of the base sheet. Since the plurality of printing dots are provided as the anti-sticking portions, the other optical elements are brought into contact with each other in the plurality of printing dots. Therefore, the optical sheet can prevent sticking with other members arranged on the back side. Further, since the optical sheet prevents sticking by a plurality of printed dots, unlike the anti-sticking layer in which the beads are dispersed in the conventional binder, the base sheet of the optical sheet and / It is possible to prevent the occurrence of scratches on the member.

The average diameter of the printed dots is preferably 1 占 퐉 or more and 200 占 퐉 or less. This makes it possible to easily and reliably form printed dots having sufficient sticking performance and adhesive strength.

The ratio of the average height of the printed dots to the average diameter is preferably 1/100 or more to 1 or less. As a result, printed dots having sufficient sticking performance and adhesive strength can be easily and reliably formed.

The printing dot may be a flat hemispherical shape whose height direction is shorter than the diameter direction. As a result, printed dots having sufficient sticking performance and adhesive strength can be easily and reliably formed.

The present density of the printed dots on the back surface of the base sheet is preferably 10 / mm ² to 2500 / mm ² . As a result, the optical sheet can exhibit a sticking performance suitable for a plurality of printed dots.

The main component of the printed dot may be an acryl-based, urethane-based or acrylic urethane-based resin. This makes it easy to form printed dots accurately.

The substrate sheet may have a base layer and another functional layer arranged on the back surface of the base layer, and the printing dot may be formed on the back surface of the functional layer. As a result, since the functional layer is arranged on the back surface of the base layer and is not directly exposed, the occurrence of scratches on the base layer can be prevented.

The functional layer may be an antistatic layer. As a result, it is possible to suppress the occurrence of scratches on the surface of the other member due to adhesion of foreign matter, and to further improve the scratch-preventive property.

And a light diffusing layer laminated on the surface side of the substrate sheet, and the light diffusing layer may have a light diffusing agent and a binder. As a result, light rays incident from the back surface side can be diffused and emitted substantially uniformly from the surface side.

The average height of the printed dots is preferably larger than the average particle diameter of the light diffusing agent. As a result, it is possible to suppress mirror surface reflection on the back surface by the anti-sticking portion, to effectively receive light from the back surface, to diffuse the received light in the light diffusion layer, and to exit from the surface side.

The average diameter of the printed dot is preferably not less than 2 times and not more than 20 times the average particle diameter of the light diffusing agent. As a result, the incident angle of the light from the back surface of the anti-stick portion is adjusted appropriately, and light can be effectively received from the back surface.

Further, an edge light type backlight unit according to the present invention performed to solve the above-described problems includes the optical sheet having the above-described structure, and a light guide plate arranged on the back side of the optical sheet. Therefore, in the backlight unit, the optical sheet is brought into contact with the light guide sheet by the plurality of printing dots, and the sticking of the optical sheet and the light guide sheet can be prevented.

The light guide plate may have a plurality of concave portions arranged to be substantially parallel to the surface. As a result, the light guideability in the mounting direction of the concave treads of the light guide plate is improved, and the uniformity of light emission in the plane direction of the backlight unit can be easily and reliably realized.

And the average diameter of the printed dots may be equal to or greater than the average width of the recessed treads. As a result, it is possible to inhibit the printed dots from entering the recessed groove portion, so that the optical sheet can exhibit the sticking prevention function more reliably by the printed dot.

The optical sheet may also be an edge light type light guide sheet for a backlight unit that emits light beams incident from the end face to the surface. Thus, since the optical sheet is an edge light type light guide sheet for a backlight unit, it is possible to prevent sticking to other members such as a reflection sheet and a top plate arranged on the back side of the optical sheet. Further, since the optical sheet prevents sticking by a plurality of printed dots, unlike the sticking prevention layer in which the beads are dispersed in the conventional binder, the optical sheet is damaged due to scratches on the surface of the reflective sheet or the top plate Can be prevented.

The printed dot may contain a white pigment. As a result, light rays incident from the end face can be propagated in the base layer, efficiently scattered by a plurality of printed dots, and emitted from the surface side.

The substrate sheet may have a wave-like fine modulation structure on its surface. As a result, light transmittance, diffusibility, or light emitting properties are promoted, and the luminance of the light ray emitted from the surface of the optical sheet and deterioration of the uniformity thereof can be suppressed. Specifically, when the ridgeline direction of the fine modulation structure of the optical sheet and the incident direction of the light beam are provided substantially parallel to each other, the transmitted light beam is likely to be condensed on the ridgeline side due to the fine modulation structure of the wave, And the diffusibility of the outgoing light can be improved because the light emitted from the surface is slightly diffused in the direction perpendicular to the ridgeline by the refraction in the fine modulation structure of the wave. On the other hand, when the ridgeline direction and the incident direction of the light beam in the fine modulation structure of the optical sheet are set to be substantially perpendicular, the incident angle of the light beam to the surface varies due to the fine modulation structure of the wave phase, Emitting performance can be improved.

Further, an edge light type backlight unit according to the present invention performed to solve the above problems comprises the optical sheet as a light guide sheet for an edge light type backlight unit. Therefore, in the backlight unit, the optical sheet is brought into contact with other members arranged on the back surface of the optical sheet by a plurality of printing dots, and sticking of the back surface of the optical sheet can be prevented.

In the present invention, " front side " means the viewer side of the liquid crystal display device, and " back side " The " diameter " of the printed dot means an intermediate value between the maximum diameter and the minimum diameter of the base of the printed dot (the surface in contact with the base sheet). The " average diameter " of the printed dot refers to an average value of 10 diameters except for five arbitrary 20 printed dots and five diameters from the larger diameter and five diameters from the smaller diameters. The " average height " of the printed dots is an average value of the heights of any ten printed dots. Refers to a shape obtained by compressing a sphere in one axial direction and cutting it in half along the vertical direction of the compression direction, and " roughly semi-spherical " means not only a complete flat semi-spherical shape, And the tangential direction of each side of the side surface is 90 DEG or less (the angle at which the printed dot is present is 90 DEG or less), and the tangential direction of the side surface is gradually shifted from the base side to the top, But also shapes that become parallel. The term " substantially parallel " includes not only the complete parallelism but also the case where the angle between the concave portions is 10 DEG or less, preferably 5 DEG or less. The " width " of the concave trough means a value obtained by dividing the area (the area of the opening portion) of each concave trough by the length of the concave trough. The "average width" of the concave-convex portion refers to an average value of 10 widths, excluding arbitrary twenty concave portions, five of which are large and five of which are small. The " density of printed dots " refers to a value calculated by calculating the number of printed dots in the field of view observed by magnifying it 1000 times with a laser microscope and using the visual field area. The " main component " refers to a component having the highest content, for example, a component having a content of 50 mass% or more.

INDUSTRIAL APPLICABILITY As described above, the optical sheet and the edge light type backlight unit of the present invention can prevent sticking of the optical sheet and other members arranged on the back side of the optical sheet, It is possible to prevent the occurrence of scratches.

Fig. 1 is a schematic sectional view (a) showing an edge light type backlight unit according to the first embodiment of the present invention, a schematic sectional view (b) showing an optical sheet included in the edge light type backlight unit, (C) is a schematic partial enlarged view of the back surface of the sheet.
Fig. 2 is a schematic enlarged view showing the arrangement state of the optical sheet and the light guide plate of the backlight unit of Fig. 1;
Fig. 3 is an explanatory diagram of the light receiving function of the optical sheet of Fig. 1;
4 is a schematic cross-sectional view showing an optical sheet according to a different embodiment from the optical sheet of Fig.
5 is a schematic cross-sectional view showing an edge light type backlight unit according to a different form from the edge light type backlight unit of FIG.
6 is a schematic perspective view (a) showing a conventional edge light type backlight unit and a schematic sectional view (b) showing a conventional light diffusion sheet.

(Mode for carrying out the invention)

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings appropriately.

[First Embodiment]

<Edge light type backlight unit>

An edge light type backlight unit 1 of Fig. 1 (a) includes an optical sheet 2, a light guide plate 3, a reflection sheet 4, and a light source 5.

(Optical sheet)

1 (b), the optical sheet 2 includes a base sheet 6, a light diffusion layer 7 laminated on the surface of the base sheet 6, And an anti-sticking portion 8 arranged in an array.

(Substrate sheet)

The base sheet 6 is required to transmit light rays and is made of a transparent resin, particularly a colorless transparent synthetic resin. The synthetic resin used for the substrate sheet 6 is not particularly limited and examples thereof include polyethylene terephthalate, polyethylene naphthalate, acrylic resin, polycarbonate, polystyrene, polyolefin, cellulose acetate, weather-resistant vinyl chloride, have. Among them, polyethylene terephthalate having excellent transparency and high strength is preferable, and polyethylene terephthalate having improved bending performance is particularly preferable.

The lower limit of the average thickness of the base sheet 6 is preferably 10 占 퐉, more preferably 35 占 퐉, and even more preferably 50 占 퐉. On the other hand, the upper limit of the average thickness of the base sheet 6 is preferably 500 占 퐉, more preferably 250 占 퐉, and further preferably 188 占 퐉. When the average thickness of the substrate sheet 6 is less than the lower limit described above, there is a fear that curling may occur when the light diffusion layer 7 and the anti-sticking portion 8 are formed by coating. On the contrary, when the average thickness of the base sheet 6 exceeds the upper limit, there is a fear that the brightness of the liquid crystal display device is lowered, and the thickness of the backlight unit 1 is increased to satisfy the demand for thinning of the liquid crystal display device There is a possibility that it can not be done.

(Light diffusion layer)

The light diffusion layer 7 is laminated on the surface of the base material sheet 6. [ The light diffusing layer 7 has a light diffusing agent 9 and a binder 10 thereof. The light diffusing layer 7 disperses the light diffusing agent 9 at substantially the same density. The light diffusing agent 9 is surrounded by the binder 10. The light diffusing layer 7 disperses the light diffusing agent 9 in a substantially uniform manner by dispersing the light diffusing agent 9 therein. The light diffusing layer 7 is formed by the light diffusing agent 9 with fine irregularities on the surface almost uniformly, and the concave portions and convex portions of the fine irregularities are formed into a lens shape. The light diffusing layer 7 exhibits an excellent light diffusing function due to the lens-like action of the fine irregularities and has a refracting function of refracting the transmitted light ray in the normal direction side due to the light diffusing function, As shown in FIG.

The light diffusing agent 9 is a particle having a property of diffusing a light ray, and is generally divided into an inorganic filler and an organic filler. Examples of the inorganic filler include silica, aluminum hydroxide, aluminum oxide, zinc oxide, barium sulfide, magnesium silicate, and mixtures thereof. Specific examples of the organic filler include acrylic resin, acrylonitrile resin, polyurethane, polyvinyl chloride, polystyrene, polyamide, and polyacrylonitrile. Among them, an acrylic resin having high transparency is preferable, and polymethyl methacrylate (PMMA) is particularly preferable.

The shape of the light diffusing agent 9 is not particularly limited and examples thereof include a spherical shape, a cubic shape, a needle shape, a rod shape, a spindle shape, a plate shape, a scaly shape and a fibrous shape. Among them, Of beads are preferable.

The lower limit of the average particle diameter of the light diffusing agent 9 is preferably 1 占 퐉, more preferably 2 占 퐉, and further preferably 5 占 퐉. On the other hand, the upper limit of the mean particle size of the light diffusing agent 9 is preferably 50 占 퐉, more preferably 20 占 퐉, and further preferably 15 占 퐉. If the average particle diameter of the light diffusing agent 9 is less than the above lower limit, the unevenness of the surface of the light diffusion layer 7 formed by the light diffusion agent 9 becomes small, There is a concern. On the other hand, when the average particle diameter of the light diffusing agent 9 exceeds the upper limit, the thickness of the optical sheet 2 may increase, and uniform diffusion may become difficult.

The lower limit of the blending amount of the light diffusing agent 9 (blending amount in terms of solid content relative to 100 parts by mass of the polymer component in the polymer composition as the forming material of the binder 10) is preferably 10 parts by mass, more preferably 20 parts by mass, More preferred is the addition. On the other hand, the upper limit of the amount of the light diffusing agent 9 (the blending amount in terms of solid content relative to 100 parts by mass of the polymer in the polymer composition as the material for forming the binder 10) is preferably 500 parts by mass, more preferably 300 parts by mass, More preferably 200 parts by mass. If the blending amount of the light diffusing agent 9 is less than the above lower limit, the light diffusibility may be insufficient. Conversely, when the compounding amount of the light diffusing agent 9 exceeds the upper limit, there is a fear that the light diffusing agent 9 is not fixed accurately by the binder 10. However, when the optical sheet 2 is used as a so-called upper light diffusing sheet arranged on the front surface side of the prism sheet, high light diffusing properties are not required, and therefore the lower limit of the compounding amount of the light diffusing agent 9 Is preferably 5 parts by mass, more preferably 10 parts by mass, and the upper limit is preferably 40 parts by mass, more preferably 30 parts by mass.

The binder 10 is formed by curing (crosslinking, etc.) the polymer composition containing the base polymer. The light diffusing agent 9 is fixed by the binder 10 to the entire surface of the substrate sheet 6 at substantially the same density. In addition, the polymer composition for forming the binder 10 may further contain a filler such as a micro inorganic filler, a curing agent, a plasticizer, a dispersant, various leveling agents, an antistatic agent, an ultraviolet absorber, an antioxidant, a viscous modifier, And the like may be appropriately blended.

(Sticking prevention part)

The optical sheet 2 has a plurality of printing dots as the anti-sticking portion 8. That is, in the optical sheet 2, the sticking prevention portion 8 is constituted by a plurality of printing dots. Therefore, the optical sheet 2 abuts against the light guide plate 3, which is superimposed on the back surface of the optical sheet 2 as described below, in a scattered manner by a plurality of printed dots, Sticking with the light guide plate 3 can be prevented. The plurality of printing dots are arranged in a scattered manner over the entire surface of the substrate sheet 6, and are arranged substantially evenly on the back surface of the substrate sheet 6. [

The plurality of printing dots include a binder component as a main component. Examples of the binder component include a thermosetting resin and an active energy ray-curable resin.

Examples of the thermosetting resin include epoxy resins, silicone resins, phenol resins, urea resins, unsaturated polyester resins, melamine resins, alkyd resins, polyimide resins, acrylic resins, amide functional copolymers, .

Examples of the active energy ray curable resin include an ultraviolet curable resin which is crosslinked and cured by irradiation with ultraviolet rays and an electron beam curable resin which is crosslinked and cured by irradiating with an electron beam and which is appropriately selected from polymerizable monomers and polymerizable oligomers It is possible. Among them, the active energy ray-curable resin is preferably an acrylic resin, a urethane resin or an acrylic urethane-based ultraviolet curable resin. In the optical sheet 2, since the main component of the printed dot is acrylic, urethane-based, or acrylic urethane-based ultraviolet curable resin, adhesion of the printed dot to the substrate sheet 6 is improved, .

As the polymerizable monomer, a (meth) acrylate-based monomer having a radically polymerizable unsaturated group in the molecule is suitably used, and among these, a multi-functional (meth) acrylate is preferable. The polyfunctional (meth) acrylate is not particularly limited as long as it is a (meth) acrylate having two or more ethylenic unsaturated bonds in the molecule. Specific examples include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6- Acrylate, neopentylglycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, hydroxypivalic neopentylglycol di (meth) acrylate, dicyclopentanyl di Acrylate, caprolactone-modified dicyclopentenyl di (meth) acrylate, ethylene oxide modified phosphoric acid di (meth) acrylate, allylated cyclohexyl di (meth) acrylate, isocyanurate di (meth) Trimethylolpropane tri (meth) acrylate, ethylene oxide modified trimethylol propane tri (meth) acrylate, dipentaerythritol tri (Meth) acrylate, propylene oxide-modified tri (meth) acrylate, propionic acid-modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (Meth) acrylate, dipentaerythritol hexa (meth) acrylate, ethylene oxide modified dipentaerythritol hexa (metha) acrylate, caprolactone-modified dipentaerythritol hexa (Meth) acrylate, and the like. These multifunctional (meth) acrylates may be used singly or in combination of two or more. Among them, dipentaerythritol tri (meth) acrylate is preferable.

In addition to the above-mentioned multi-functional (meth) acrylate, a monofunctional (meth) acrylate may further be contained for the purpose of lowering the viscosity. Examples of the monofunctional (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl Acrylate, isooctyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl . These monofunctional (meth) acrylates may be used alone or in combination of two or more.

Examples of the polymerizable oligomer include an oligomer having a radically polymerizable unsaturated group in the molecule, and examples thereof include an epoxy (meth) acrylate oligomer, a urethane (meth) acrylate oligomer, a polyester (meth) Based oligomers, polyether (meth) acrylate-based oligomers, and the like.

The epoxy (meth) acrylate oligomer can be obtained, for example, by reacting (meth) acrylic acid with an oxirane ring of a relatively low molecular weight bisphenol type epoxy resin or novolac type epoxy resin to effect esterification. It is also possible to use an epoxy (meth) acrylate oligomer whose carboxyl-modified epoxy is partially modified with a dibasic carboxylic acid anhydride. The urethane (meth) acrylate oligomer is obtained by, for example, esterifying a polyurethane polyol or a polyurethane oligomer obtained by the reaction of a polyester polyol and a polyisocyanate with (meth) acrylic acid Can be obtained. The polyester (meth) acrylate oligomer can be obtained by, for example, esterifying a hydroxyl group of a polyester oligomer having a hydroxyl group at both terminals obtained by condensation of a polyvalent carboxylic acid and a polyhydric alcohol with (meth) acrylic acid. The polyester (meth) acrylate oligomer can also be obtained by esterifying the terminal hydroxyl group of an oligomer obtained by adding an alkylene oxide to a polyvalent carboxylic acid with (meth) acrylic acid. The polyether (meth) acrylate oligomer can be obtained by esterifying the hydroxyl group of the polyether polyol with (meth) acrylic acid.

As the active energy ray curable resin, an ultraviolet curable epoxy resin is also suitably used. Examples of the ultraviolet curable epoxy resin include cured products such as bisphenol A type epoxy resin and glycidyl ether type epoxy resin. Since the binder component of the plurality of printing dots is an ultraviolet curable epoxy resin, the optical sheet (2) is capable of suppressing volume shrinkage upon curing and easily form a plurality of printed dots into a desired shape such as semi-spherical shape. In addition, since the binder component of the plurality of printing dots is an ultraviolet curing type epoxy resin, the optical sheet 2 can be improved in flexibility of a plurality of printing dots, and the wrinkles on other members arranged on the back surface of the anti- And the generation prevention property can be improved. When an ultraviolet curable epoxy resin is used as the active energy ray-curable resin, it is preferable that the resin does not contain any other polymerizable monomer such as the (meth) acrylate-based monomer and the (meth) acrylate-based oligomer and the polymerizable oligomer Do. This makes it possible to further enhance the flexibility of the plurality of printing dots and further promote the scratch prevention property.

When an ultraviolet curable resin is used as the active energy ray curable resin, it is preferable to add about 0.1 to 5 parts by mass of the photopolymerization initiator to 100 parts by mass of the resin. The initiator for photopolymerization is not particularly limited, and examples of the polymerizable monomer having a radically polymerizable unsaturated group in the molecule and the polymerizable oligomer include benzophenone, benzyl, Michler's ketone, 2-chlorothioxanthone, 4-diethyl thioxanthone, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-diethoxyacetophenone, benzyl dimethyl ketal, 2,2-dimethoxy 2-methyl-1-phenylpropan-1-one, 1-hydroxychlorohexyl phenyl ketone, 2-methyl- Phenyl] -2-hydroxy-2-methyl-1-propan-1-one &lt; / RTI &gt; , Bis (cyclopentadienyl) -bis (2,6-difluoro-3- (pil-1-yl) titanium, 2-benzyl- ) -Butanone-l, 2,4,6-trimethylbenzoyldiphenylphosphine oxide Etc. Further, examples of the polymerizable oligomer having a cationic polymerizable functional group in the molecule include an aromatic sulfonium salt, an aromatic diazonium salt, an aromatic iodonium salt, a metallocene compound, a benzoin sulfonic acid ester, and the like. These compounds may be used individually or in combination.

It is also possible that the printing dot includes an additive in addition to the binder component. Examples of the additive include silicon-based additives, fluorine-based additives, and antistatic agents. The content of the additive in terms of solid content relative to 100 parts by mass of the binder component may be, for example, 0.05 parts by mass or more and 5 parts by mass or less.

The plurality of printing dots are formed by a printing method using ink for printing dots containing a binder component.

Examples of the printing method include a screen printing method, an inkjet printing method, a gravure printing method, an offset method, a flexo printing method, and a dispenser printing method. Among them, offset printing capable of forming printing dots of small diameter with high precision, flexography printing capable of forming printing dots of small diameter with high precision, or screen printing capable of forming thick printing dots by thickening the ink is preferable .

As shown in Fig. 1 (c), the printed dot is formed in a substantially circular shape when viewed from the rear side. The term &quot; approximately circular &quot; includes not only a complete circle but also circular arc, and the maximum diameter (the largest of the lengths of the imaginary straight line passing through the center) is the minimum diameter Of the length of the straight line), preferably 1.5 times or less.

The lower limit of the average diameter d of the printed dots is preferably 1 占 퐉, more preferably 3 占 퐉, further preferably 10 占 퐉, and particularly preferably 20 占 퐉. On the other hand, the upper limit of the average diameter d of the printed dots is preferably 200 占 퐉, more preferably 100 占 퐉, and even more preferably 50 占 퐉. If the average diameter d of the printed dots is less than the above lower limit, there is a fear that the adhesiveness with the base sheet 6 is lowered. Conversely, when the average diameter d of the printed dots exceeds the upper limit, the printed dots become unnecessarily large, which may adversely affect the optical characteristics of the backlight unit.

It is preferable that the average diameter d of the printed dots is not less than an average width w2 of the concave trough 11 of the light guide plate 3 to be described later. Since the average diameter d of the printed dots is equal to or greater than the average width w2 of the concave trough 11, it is possible to suppress the penetration of the printed dots into the concave trough 11. For this reason, the optical sheet 2 can exhibit the sticking prevention function more reliably by the printing dot. The lower limit of the ratio (d / w2) of the average diameter d of the printed dots to the average width w2 of the concave trough 11 is preferably 1.05, more preferably 1.1, and further preferably 1.2. As a result, it is possible to more reliably prevent the printed dots from entering the concave trough 11. The upper limit of the ratio (d / w2) of the average diameter d of the printed dots to the average width w2 of the concave trough 11 is not particularly limited and is, for example,

The lower limit of the average height h of the printed dots is preferably 0.5 占 퐉, more preferably 1 占 퐉, further preferably 3 占 퐉, and particularly preferably 5 占 퐉. On the other hand, the upper limit of the average height h of the printed dots is preferably 100 m, more preferably 50 m, and further preferably 10 m. If the average height (h) of the printed dots is less than the lower limit, sticking can not be sufficiently prevented. Conversely, when the average height h of the printed dots exceeds the upper limit, it is difficult to form the printed dots and the productivity may be lowered.

It is preferable that the plurality of printed dots have a uniform height. That is, the upper limit of the coefficient of variation of the height h of the printed dot is preferably 0.2, more preferably 0.1, and still more preferably 0.05. If the coefficient of variation of the height h of the printed dot exceeds the upper limit, the heights of the plurality of printed dots become uneven, the load is imposed on the thick printed dot, . The lower limit of the coefficient of variation of the height h of the printed dot is not particularly limited and may be zero, for example. The &quot; variation coefficient &quot; of the height of the printed dot is a value obtained by dividing the standard deviation of the height of the plurality of printed dots by the average height.

The lower limit of the height ratio (h / d) to the average diameter d of the average height h of the printing dots is preferably 1/100, more preferably 1/20, and further preferably 1/10. When the height ratio (h / d) is less than the lower limit, there is a fear that the printed dot becomes unnecessarily large.

The upper limit of the height ratio (h / d) to the average diameter d of the average height h of the printing dots is preferably 1. When the height ratio (h / d) exceeds the upper limit, the contact surface of the printed dot with respect to the other member becomes sharp, and the occurrence of scratches on other members arranged on the back side of the anti- There is a fear that the property may deteriorate. The upper limit of the height ratio (h / d) to the average diameter d of the average height h of the printing dots is more preferably 1/2, and still more preferably 1/5. As a result, the contact area between the printed dot and the substrate sheet 6 is widened, and the adhesion between the printed dot and the substrate sheet 6 is excellent.

The shape of the printed dot is preferably semi-spherical, more preferably a flat semi-spherical shape having a shorter height direction than the diameter direction. Since the printed dot is formed in the flat semi-spherical shape, sticking can be suitably prevented, and since the contact surface with the surface of the light guide sheet 3 is a gently curved surface, .

The average height (h) of the printed dots is preferably larger than the average particle diameter of the light diffusing agent (9). The lower limit of the ratio of the height h of the printed dot to the average particle diameter of the light diffusing agent 9 is more preferably 6/5 and further preferably 3/2. On the other hand, the upper limit of the ratio of the height h of the printed dot to the average particle diameter of the light diffusing agent 9 is preferably 4, more preferably 3, and still more preferably 2. When the ratio of the height h of the printed dot to the mean particle diameter of the light diffusing agent 9 is less than the lower limit, the printing dot becomes too flat, and the printing dot is sufficiently received There is a possibility that it can not be done. Conversely, when the ratio of the height h of the printed dot to the mean particle diameter of the light diffusing agent 9 exceeds the upper limit, the printed dot becomes excessively sharp and the light incident on the printed dot from the back side There is a fear that it will not be accepted sufficiently.

The lower limit of the ratio of the average diameter (d) of the printed dot to the average particle diameter of the light diffusing agent (9) is preferably 2, more preferably 3, and further preferably 4. On the other hand, the upper limit of the ratio of the average diameter (d) of the printed dot to the average particle diameter of the light diffusing agent (9) is preferably 20, more preferably 15, When the ratio of the average diameter d of the printed dots to the average particle diameter of the light diffusing agent 9 is less than the lower limit described above, the printed dot becomes excessively sharp, and light incident on the printed dot from the back side is sufficiently received There is a fear that they will not be able to enter. Conversely, when the ratio of the average diameter d of the printed dots to the average particle diameter of the light diffusing agent 9 exceeds the upper limit, the printed dot becomes excessively flat, There is a fear that the light can not be sufficiently received.

The plurality of printing dots are arranged substantially uniformly on the back surface of the substrate sheet 6 as described above. The lower limit of the average pitch of the plurality of printing dots is preferably 20 占 퐉, more preferably 30 占 퐉, and even more preferably 40 占 퐉. On the other hand, the upper limit of the average pitch of the printed dots is preferably 300 mu m, more preferably 150 mu m, and further preferably 70 mu m. If the average pitch of the printed dots is less than the lower limit, the number of printed dots is excessively large, which may adversely affect the optical characteristics of the backlight unit. Conversely, when the average pitch of the printed dots exceeds the upper limit, there is a possibility that the sticking-preventing effect may not be sufficiently obtained.

The lower limit of the existence density of the dots printed on the back surface of the base material sheet (6) as 10 / mm ² is preferred, and, and 60 / mm ² is more preferred, and 100 / mm ^2, more preferably 200 / mm &lt; ² &gt; is particularly preferable. On the other hand, as the upper limit of the existence density of the dots printed on the back surface of the base material sheet 6 2500 / mm ² it is preferred, and 1000 lines / mm and ² are more preferred, 600 / mm ² is more preferable, and 450 / Mm &lt; ² &gt; is particularly preferable. If the density of the printed dots is less than the lower limit, there is a possibility that the anti-sticking effect may not be sufficiently obtained. Conversely, when the density of the printed dots exceeds the upper limit, there is a high possibility that scratches are generated on the surface of the other member arranged on the back side.

(Light guide plate)

The light guide plate 3 is a sheet-like optical member which is emitted from the surface while propagating the light beam emitted from the light source 5 inside. The light guide plate 3 may be formed in a substantially wedge shape in section, or may be formed as a substantially flat light guide sheet. Since the light guide plate 3 needs to have translucency, it is formed with a transparent, particularly colorless transparent resin as a main component. The main component of the light guide plate 3 is not particularly limited, but includes synthetic resins such as polycarbonate excellent in transparency and strength, acrylic resin excellent in transparency, scratch resistance, and the like. Among them, polycarbonate is preferable as the main component of the light guide plate 3. Since the polycarbonate is excellent in transparency and has a high refractive index, the polycarbonate is arranged in the air layer (a layer formed in the gap with the optical sheet 2 arranged on the front surface side of the light guide plate 3 and on the back side of the light guide plate 3 (The layer formed in the gap with the reflective sheet 4), the light can be efficiently propagated. Further, since polycarbonate has heat resistance, deterioration due to heat generation of the light source 5 is less likely to occur.

As shown in Fig. 2, the light guide plate 3 has a plurality of concave troughs 11 arranged substantially parallel to the surface. Concretely, grooves are formed on the surface of the light guide plate 3 as the concave trough 11. The shape of the cross section of the concave trough 11 (shape cut perpendicularly to the direction in which the concave trough 11 is arranged) is not particularly limited, and examples thereof include a V shape, a U shape, and a C shape. Among them, the cross-sectional shape of the concave trough 11 is preferably a V-shaped shape which tends to improve the light guideability of the light guide plate 3. The direction in which the concave trough portions 11 are arranged may be substantially parallel to the end surface on the light source 5 side, or may be substantially perpendicular. The light guide plate 3 has a plurality of concave trough portions 11 arranged substantially in parallel to the surface so as to improve the light guideability in the direction in which the concave trough portions 11 are arranged and improve the light transmittance of the backlight unit 1 in the plane direction Uniformity of light emission can be easily and reliably realized. Also, the light guide plate 3 may have all the concave troughs 11 of the same size and the same shape, and also have the concave troughs 11 of different sizes or different shapes.

The lower limit of the average width w1 of the concave trough 11 is preferably 5 占 퐉, more preferably 10 占 퐉, and even more preferably 20 占 퐉. On the other hand, the upper limit of the average width w1 of the concave trough 11 is preferably 50 占 퐉, more preferably 40 占 퐉, and further preferably 35 占 퐉. When the average width w1 of the concave trough 11 is less than the lower limit, there is a possibility that the light guideability of the light guide plate 3 may not be sufficiently increased. Conversely, when the average width w1 of the concave trough 11 exceeds the upper limit, there is a possibility that desired optical characteristics may not be obtained.

The lower limit of the average interval w2 of the concave troughs 11 is preferably 10 占 퐉, more preferably 20 占 퐉, and further preferably 30 占 퐉. On the other hand, the upper limit of the average interval w2 of the concave troughs 11 is preferably 300 占 퐉, more preferably 200 占 퐉, and even more preferably 100 占 퐉. If the average interval w2 of the concave troughs 11 is less than the lower limit, the desired optical characteristics may not be obtained. Conversely, if the average interval w2 of the concave troughs 11 exceeds the upper limit, there is a possibility that the light guideability of the light guide plate 3 may not be sufficiently high. Means the distance between the concave trough 11 and the adjacent concave trough 11 (the distance between the centers of the concave trough 11), and the "distance" between the concave trough 11 and the adjacent concave trough 11, Means the average value of 10 values obtained by extracting the widths of arbitrary 20 concave troughs and excluding 5 from the larger value and 5 from the smaller value.

The lower limit of the average depth of the concave trough 11 is preferably 2 占 퐉, more preferably 4 占 퐉, and further preferably 6 占 퐉. On the other hand, the upper limit of the average depth of the concave trough 11 is preferably 30 占 퐉, more preferably 20 占 퐉, and further preferably 10 占 퐉. When the average depth of the concave trough 11 is less than the lower limit, there is a possibility that the light guide property of the light guide plate 3 may not be sufficiently high. Conversely, when the average depth of the concave trough 11 exceeds the upper limit, there is a possibility that the desired optical characteristics may not be obtained. The depth of the concave trough 11 means the distance from the average interface of the surface of the light guide plate 3 to the bottom (deepest position) of the concave trough 11, Refers to an average value of 10 depths, excluding five, from five depths and five small depths, of arbitrary 20 concave troughs.

The lower limit of the ratio of the average depth of the recessed trough 11 to the average thickness of the light guide plate 3 is preferably 0.001, more preferably 0.005, and still more preferably 0.01. On the other hand, the upper limit of the ratio of the average depth of the recessed trough 11 to the average thickness of the light guide plate 3 is preferably 0.15, more preferably 0.1, and still more preferably 0.05. When the ratio of the average depth of the concave trough 11 to the average thickness of the light guide plate 3 does not reach the lower limit, there is a possibility that the light guide property of the light guide plate 3 may not be sufficiently high. Conversely, when the ratio of the average depth of the concave trough portion 11 to the average thickness of the light guide plate 3 exceeds the upper limit, there is a possibility that desired optical characteristics may not be obtained.

(Reflective sheet)

The reflective sheet 4 reflects the light beam emitted from the back side of the light guide plate 3 to the surface side. As the reflective sheet 4, a metal such as aluminum or silver is deposited on the surface of a film formed of a white sheet in which a filler is dispersedly contained in a base resin such as a polyester resin, or a polyester resin or the like, And a mirror-surface sheet.

(Light source)

The light source 5 is arranged so that the irradiation surface faces (or comes into contact with) the end surface of the light guide plate 3. A variety of light sources 5 can be used, and for example, light emitting diodes (LEDs) can be used. Specifically, as this light source 5, a plurality of light emitting diodes arranged along the end face of the light guide plate 3 can be used.

<Function of accepting light>

The function of accepting light emitted from the surface of the light guide plate 3 will be described with reference to Fig. Since the plurality of light emitting diodes used as the light source 5 are strong in directivity, light having high intensity in a certain direction (for example, about 60 degrees with respect to the normal direction) is emitted from the surface of the light guide plate 3. The light emitted from the surface of the light guide plate 3 is incident on the back surface of the optical sheet 2. In the conventional sticking preventing layer, most of the light having a high intensity in the predetermined direction as described above, (Refer to FIG. 3 (b)). Therefore, the light amount of the normal direction component among the light emitted from the surface of the light guide plate 3 becomes large.

On the other hand, the anti-sticking portion 8 of the optical sheet 2 has a comparatively large average diameter of the printed dots and is formed of a relatively gentle curved surface, such as a flat semi-spherical surface, The light emitted from the light source is likely to be received. That is, since the anti-sticking portion 8 has the constant curved surface on the back surface, there are many portions close to 90 degrees with respect to light in a certain direction emitted from the surface of the light guide plate 3, Is difficult to be reflected. Therefore, the optical sheet 2 can efficiently receive strong light in a certain direction emitted from the surface of the light guide plate 3 by the anti-sticking portion 8 (see Fig. 3 (a)).

&Lt; Production method of optical sheet >

The optical sheet 2 can be produced by, for example, (1) applying the material for forming the light diffusion layer 7 to the surface of the substrate sheet 6, and drying and curing the light diffusion layer 7, (2) applying ink for printing dots on the back surface of the substrate sheet 6 by a printing method such as screen printing, flexographic printing or offset printing, and drying and curing the printing ink, (8) on the back surface of the substrate sheet (6).

<Advantages>

The optical sheet 2 is provided with the anti-sticking portions 8 on the back surface of the substrate sheet 6 and has a plurality of printed dots as the anti-sticking portions 8, The light guide plate 3 and the plurality of printing dots are abutted against each other. Therefore, the optical sheet 2 can be prevented from sticking to the light guide plate 3 arranged on the back side. In addition, since the optical sheet 2 prevents sticking by a plurality of printed dots, unlike the sticking prevention layer in which beads are dispersed in the conventional binder, the optical sheet 2 has a problem that the surface of the light guide plate 3, The occurrence of scratches on the back surface of the optical sheet 2 can be prevented.

The optical sheet 2 has a light diffusing layer 7 laminated on the surface side of the substrate sheet 6. Since the light diffusing layer 7 has the light diffusing agent 9 and the binder 10, It is possible to diffuse the light beam incident from the back side and emit substantially uniformly from the front side.

Since the edge light type backlight unit 1 includes the optical sheet 2 as described above, sticking of the optical sheet 2 to the light guide plate 3 arranged on the back side can be prevented And the occurrence of scratches on the surface of the light guide plate 3 can be prevented. In addition, the edge light type backlight unit 1 has improved scratch resistance on the surface of the light guide plate 3 by the optical sheet 2, and therefore improves handling in assembling the backlight unit.

[Second Embodiment]

<Optical sheet>

The optical sheet 21 of FIG. 4 is used in the edge light type backlight unit 1 instead of the optical sheet 2 of FIG. The optical sheet 21 includes a base sheet 22, a light diffusion layer 7 laminated on the surface of the base sheet 22, and a sticking prevention portion 24 arranged on the back surface of the base sheet 22 do. The base sheet 22 has a base layer 6 and another functional layer laminated on the back surface of the base layer 6, and the printing dots are formed on the back surface of the functional layer. In the present embodiment, the functional layer is an antistatic layer 23. Specifically, the base sheet 22 is formed as a two-layer structure (multilayer structure) of a base layer 6 and an antistatic layer 23 arranged on the back surface of the base layer 6. [ Since the base layer 6 is the same as the base sheet 6 of Fig. 1, the same reference numerals are given thereto, and a description thereof is omitted. Since the light diffusing layer 7 is the same as the optical sheet 2 in Fig. 1, the same reference numerals are given thereto and the description is omitted.

(Antistatic layer)

The antistatic layer 23 is formed by applying a coating liquid containing a binder component and an antistatic agent to the back surface of the base layer 6 and curing it. The binder component is not particularly limited, and for example, a thermosetting resin or an active energy ray-curable resin exemplified in the binder component of the printing dot in the optical sheet (2) in Fig. 1 can be used. Examples of the antistatic agent include, but are not limited to, anionic antistatic agents such as alkylsulfates and alkylphosphates, cationic antistatic agents such as quaternary ammonium salts and imidazoline compounds, polyethylene glycol, polyoxyethylene Nonionic antistatic agents such as sorbitan monostearic acid ester and ethanol amides, and polymeric antistatic agents such as polyacrylic acid.

The lower limit of the content of the antistatic agent in terms of solid content relative to 100 parts by mass of the binder component forming the antistatic layer 23 is preferably 0.5 parts by mass, more preferably 1 part by mass, further preferably 1.5 parts by mass. On the other hand, the upper limit of the content of the antistatic agent in terms of solid content in relation to 100 parts by mass of the binder component is preferably 5 parts by mass, more preferably 4 parts by mass, and further preferably 3 parts by mass. If the content of the antistatic agent is less than the lower limit, there is a possibility that the antistatic effect is not sufficiently obtained. On the other hand, when the content of the antistatic agent exceeds the upper limit, there is a possibility that the total light transmittance due to the addition of the antistatic agent is lowered or the strength is lowered.

As the surface resistance of the antistatic layer 23, the upper limit 1 × 10 ¹² Ω / □ is preferred, more preferably 1 × 10 ¹¹ Ω / □, and more preferably, 1 × ¹⁰ 10. If the surface resistance value of the antistatic layer 23 exceeds the upper limit, there is a possibility that the adhesion of the foreign matter can not be prevented definitely. The lower limit of the surface resistance value of the antistatic layer 23 is not particularly limited, but may be, for example, 1 x 10 ⁸ ? / ?.

The method of applying the coating liquid on the back surface of the base layer 6 is not particularly limited and examples thereof include a method using a roll coater, a kiss roll coater, a bar coater, a blade coater, a gravure roll coater, or the like . As a method of applying the coating liquid on the back surface of the substrate layer 6, spraying, immersion and the like may be mentioned.

As the lower limit of the coating amount (solid content conversion) of the coating liquid 0.01g / m ² and more preferably 0.05g / m ² a. On the other hand, as the upper limit of the coating amount (solid content conversion) of the coating solution is 0.5g / m ² and more preferably 0.1g / m ² is. When the coating amount of the coating liquid is less than the above lower limit, there is a possibility that a sufficient antistatic effect may not be obtained. On the other hand, when the coating amount of the coating liquid exceeds the upper limit, there is a possibility that the total light transmittance due to the coating of the antistatic agent is lowered, the printing adhesion is lowered, and the chemical contamination with other members occurs.

(Sticking prevention part)

The sticking prevention portion 24 has the same shape, size, and the like as the sticking prevention portion 8 of FIG. As the material for forming the anti-sticking portion 24, the same ink as the printing dot ink of the optical sheet 2 of Fig. 1 can be used.

<Advantages>

The optical sheet 21 has the substrate sheet 22 having the base layer 6 and other functional layers laminated on the back surface of the base layer 6 and the printing dots are formed on the back surface of the functional layer, Since the functional layer is arranged on the back surface of the layer 6 and is not directly exposed, the occurrence of scratches on the base layer 6 can be prevented.

Since the functional layer 23 of the optical sheet 21 is the antistatic layer 23, it is possible to suppress the occurrence of scratches on the surface of the light guide plate 3 or the like due to the adherence of foreign matter, .

[Third embodiment]

<Optical sheet>

The optical sheet 31 shown in Fig. 5 is formed as a light guide sheet for an edge light type backlight unit that emits light beams incident from the end face to the surface. The optical sheet 31 is used in the edge light type backlight unit 1 instead of the light guide plate 3 in Fig. Further, other optical sheets arranged on the surface side of the optical sheet 31 in the edge light type backlight unit are not particularly limited, and examples thereof include a light diffusion sheet and a prism sheet.

The optical sheet 31 includes a base sheet 32 and a sticking prevention portion 33 arranged on the back surface of the base sheet 32. [

(Substrate layer)

The substrate sheet 32 is formed in a flat plate shape having a substantially uniform thickness. The lower limit of the average thickness of the base sheet 32 is preferably 100 占 퐉, more preferably 150 占 퐉, and even more preferably 200 占 퐉. On the other hand, the upper limit of the average thickness of the base sheet 32 is preferably 600 占 퐉, more preferably 500 占 퐉, and further preferably 400 占 퐉. If the average thickness of the base sheet 32 is less than the above lower limit, there is a fear that the strength becomes insufficient and the light from the light source 5 may not be sufficiently introduced. Conversely, when the average thickness of the base sheet 32 exceeds the upper limit, there is a possibility that the backlight unit 1 may not be requested to be thinned.

The lower limit of the necessary light-guiding distance from the end surface of the base sheet 32 on the light source 5 side is preferably 7 cm, more preferably 9 cm, and further preferably 11 cm. On the other hand, the upper limit of the necessary light-guiding distance from the end surface of the base sheet 32 on the light source 5 side is preferably 25 cm, more preferably 23 cm, and further preferably 21 cm. If the necessary light-guiding distance is less than the lower limit, there is a possibility that the terminal can not be used in a large-sized terminal other than a small-sized mobile terminal. Conversely, when the necessary light-projecting distance exceeds the upper limit, when the substrate sheet 32 is used as a thin light-guiding sheet having an average thickness of 600 탆 or less, warpage tends to occur and light- . The necessary light-guiding distance from the end surface of the base sheet 32 on the light source 5 side is set such that the light ray emitted from the light source 5 and incident on the end surface of the base sheet 32 is propagated from this end surface toward the opposite end surface It refers to the distance that needs to be. Specifically, the necessary light-guiding distance from the end surface of the base sheet 32 on the light source 5 side is, for example, for a backlight unit of a unidirectional edge light type, the distance from the end surface on the light source side of the base sheet to the opposite end surface Refers to the distance from the end surface of the base sheet to the center of the base sheet for the backlight unit of both edge light type.

As the surface area of the lower limit of the base sheet (32) 150cm ² are preferred, and more preferably 180cm ^2, 200cm ² is more preferred. On the other hand, as the upper limit of the surface area of the substrate sheet 32 is preferably 840cm ² and more preferably 760cm ^2, 720cm ² is more preferred. When the surface area of the base sheet 32 is less than the above lower limit, there is a possibility that it can not be used in a large terminal other than a small mobile terminal. Conversely, when the surface area of the base sheet 32 exceeds the upper limit, warpage is likely to occur when the base sheet 32 is used as a thin film light guide sheet having an average thickness of 600 탆 or less, There is a possibility that it will not.

Since the base sheet 32 needs to transmit light rays, it is formed using a transparent, particularly colorless, transparent synthetic resin as a main component. The main component of the base sheet 32 is the same as the main component of the light guide plate 3.

On the surface of the substrate sheet 32, a wavy fine modulation structure is formed. In addition, the ridgeline direction in the wave-like fine modulation structure and the end surface on which the light beam is incident are arranged substantially parallel. Thus, since the ridgeline direction of the fine modulation structure is substantially perpendicular to the traveling direction of the light beam propagating in the base sheet 32, the incident angle of the light ray to the surface varies due to the fine modulation structure of the wave form The light output from the surface of the optical sheet 31 is improved.

The lower limit of the ridge line interval p in the fine modulation structure is preferably 1 mm, more preferably 10 mm, and further preferably 20 mm. On the other hand, the upper limit of the ridge line interval p in the fine modulation structure is preferably 500 mm, more preferably 100 mm, and further preferably 60 mm. When the ridge line interval p is less than the lower limit, there is a possibility that light rays are excessively emitted from the surface of the optical sheet 31. On the other hand, when the ridge line interval p exceeds the upper limit, there is a possibility that the effect of improving the light emitting property of the optical sheet 31 is low. Although it is preferable that all of the ridge intervals p in the fine modulation structure are within the above range, some of the ridge intervals p in the fine modulation structure may be out of the above range. In this case, The ridge line spacing of 50% or more, preferably 70% of the interval p may be within the above range.

Further, the lower limit of the average height of the ridgelines with respect to the approximate imaginary plane through which a plurality of curved lines in the fine modulation structure passes is preferably 5 占 퐉, more preferably 7 占 퐉, and further preferably 9 占 퐉 . On the other hand, the upper limit of the average height of the ridgelines with respect to the approximate imaginary plane through which a plurality of curves in the fine modulation structure pass is preferably 40 占 퐉, more preferably 20 占 퐉, and further preferably 15 占 퐉. If the average height of the ridgelines is less than the lower limit, there is a possibility that the effect of improving the light output of the optical sheet 31 is low. Conversely, when the average height of the ridgelines exceeds the upper limit, there is a fear that light rays are excessively emitted from the surface of the optical sheet 31. [

(Sticking prevention part)

The anti-sticking portion 33 is formed of a plurality of printing dots. The anti-sticking portion 33 is formed by a printing method using ink for printing dots containing a binder component. The binder component is the same as the binder component of the anti-sticking portion 8 in Fig. The printing method is the same as the printing method used for forming the sticking prevention portion 8 in Fig. The height ratio of the printed dots, the average diameter, the average height, the height ratio to the average diameter of the average heights, the average pitch, and the density existing at the back surface of the base sheet 32 are the same as those of the sticking- .

The printed dot preferably contains a white pigment dispersed therein. In the optical sheet 31, the light rays incident from the end face are propagated in the base sheet 32 by dispersing the white pigment in the printed dot, and then scattered efficiently by a plurality of printed dots to be emitted from the front surface side .

Examples of the white pigment include, but are not limited to, titanium oxide (titanium white), silica, calcium carbonate (chalk), zinc oxide (zinc oxide), lead carbonate (blanket) and barium sulfate.

The lower limit of the average particle diameter of the white pigment is preferably 100 nm, more preferably 200 nm. On the other hand, the upper limit of the average particle diameter of the white pigment is preferably 20 占 퐉, more preferably 10 占 퐉. When the average particle diameter of the white pigment is less than the above lower limit, there is a possibility that sufficient reflectivity may not be obtained. On the other hand, when the average particle diameter of the white pigment exceeds the upper limit, the dispersibility may be lowered.

The lower limit of the content of the white pigment (in terms of solid content) is preferably 70% by mass, more preferably 80% by mass. On the other hand, the upper limit of the content of the white pigment (in terms of solid content) is preferably 100% by mass, more preferably 90% by mass. When the content of the white pigment is less than the above lower limit, there is a possibility that sufficient reflectivity may not be obtained. Conversely, when the content of the white pigment exceeds the upper limit, there is a fear that the formation of the printed dot becomes difficult.

&Lt; Production method of optical sheet >

Examples of the production method of the optical sheet 31 include (1) a step of forming a base sheet 32 by an extrusion molding method, (2) a step of forming a T- (3) printing the ink for printing dots containing a white pigment on the back surface of the base sheet 32 by printing such as screen printing, flexographic printing, offset printing, and the like , And then forming the anti-sticking portion 33 by curing it.

<Advantages>

This optical sheet 31 is a light guide sheet for an edge light type backlight unit and can be prevented from sticking to other members such as a reflective sheet and a top plate arranged on the back side of the optical sheet 31. [ In addition, since the optical sheet 31 prevents sticking by a plurality of printed dots, unlike the sticking prevention layer in which beads are dispersed in a conventional binder, the optical sheet 31 has a surface such as a reflective sheet or a top plate It is possible to prevent the occurrence of scratches. In addition, since the optical sheet 31 has the anti-sticking portion 33 formed of a plurality of printed dots, it is possible to prevent the occurrence of scratches on the optical sheet 31 itself, .

In this backlight unit, the optical sheet 31 is brought into contact with a reflective sheet or a top plate arranged on the back surface of the optical sheet 31 by a plurality of printing dots, thereby preventing sticking of the back surface of the optical sheet 31 can do. Further, in the backlight unit, since the optical sheet 31 is brought into contact with the reflective sheet or the top plate by a plurality of printing dots, it is possible to prevent the occurrence of scratches of the optical sheet 31 itself in addition to the reflective sheet and the top plate , It is possible to easily and surely prevent the deterioration of light transmittance.

[Other Embodiments]

Further, the optical sheet and the edge light type backlight unit according to the present invention can be implemented in a mode in which various modifications and improvements are made in addition to the above-described aspects. For example, other layers may be arranged on the base layer and the light diffusion layer, between the base layer and the anti-sticking portion, on the surface of the light diffusion layer, and the like. When the substrate sheet has a substrate layer and another functional layer arranged on the back surface of the substrate layer, the functional layer may be, for example, a hard coat layer or the like.

The light guide plate or the light guide sheet may not necessarily be arranged on the back side of the light guide plate or the light guide sheet, and the light guide plate or light guide sheet may be directly arranged on the top plate (inner surface of the casing of the liquid crystal display). When the light guide plate or the light guide sheet is directly arranged on the top plate, the top plate is preferably formed using a plate material such as aluminum, and the surface of the top plate is preferably formed as a reflective surface.

When the optical sheet is formed as a light guide sheet, the optical sheet may not necessarily have a fine modulation structure. Further, when the optical sheet has a fine modulation structure, the ridgeline direction in the fine modulation structure and the end face on which the light ray is incident may be substantially orthogonal. As a result, when the light beam propagating in the optical sheet is reflected on the surface, the traveling direction of some of the light beams approaches the ridge line side, so that the light rays are easily condensed toward the ridge line side. Also, in addition to this, the diffusibility of the outgoing light beam is improved because the light rays emitted from the surface are slightly diffused in the direction perpendicular to the ridge direction by the refraction in the wave-form fine modulation structure.

The lower limit of the ridge line interval in the fine modulation structure is preferably 1 mm, more preferably 10 mm, and further preferably 20 mm. On the other hand, the upper limit of the ridge line interval in the fine modulation structure is preferably 500 mm, more preferably 100 mm, and further preferably 60 mm. When the ridge line interval is out of the above range, the light rays propagating in the optical sheet are difficult to be condensed on the ridge line side. Although it is preferable that all of the ridge line intervals in the fine modulation structure are within the above range, some of the ridge line intervals in the fine modulation structure may be out of the above range. In this case, Preferably, the ridge line spacing of 70% is within the above range.

Further, the lower limit of the average height of the ridgelines with respect to the approximate imaginary plane through which the plurality of curves in the fine modulation structure passes is preferably 5 占 퐉, more preferably 7 占 퐉, and further preferably 9 占 퐉. On the other hand, the upper limit of the average height of the ridgelines based on the approximate imaginary plane through which the plurality of curves in the fine modulation structure passes is preferably 40 占 퐉, more preferably 20 占 퐉, and further preferably 15 占 퐉. When the average height is out of the above range, light rays propagating in the optical sheet are difficult to be condensed toward the ridgeline side.

The edge light type backlight unit can be used for a variety of liquid crystal display devices such as portable computers such as laptop computers, smart phones, and portable information terminals such as tablet terminals.

INDUSTRIAL APPLICABILITY As described above, the optical sheet of the present invention and the edge light type backlight unit having the optical sheet of the present invention can prevent sticking with other members arranged on the back side of the optical sheet, It is suitably used for a liquid crystal display device in which luminance unevenness is suppressed.

1: Edge light type backlight unit 2: Optical sheet
3: light guide plate 4: reflective sheet
5: light source 6: substrate sheet (substrate layer)
7: light diffusion layer 8: anti-sticking part
9: light diffusion agent 10: binder
11: concave portion 21: optical sheet
22: substrate sheet 23: antistatic layer
24: sticking prevention part 31: optical sheet
32: base sheet 33: anti-sticking portion
41: Edge light type backlight unit 42: Light source
43: light guide plate 44: optical sheet
45: light diffusion sheet 46: prism sheet
47: Base layer 48: Light diffusion layer
49: anti-sticking layer 50: bead
51: Binder

Claims (18)

A transparent base sheet and a sticking prevention portion arranged on the back surface of the base sheet,
Wherein the sticking prevention portion has a plurality of printing dots. The method according to claim 1,
Wherein the average diameter of the printed dots is 1 占 퐉 or more and 200 占 퐉 or less. The method according to claim 1,
Wherein the ratio of the average height of the printed dots to the average diameter is 1/100 or more to 1 or less. The method according to claim 1,
Wherein the printing dot is a flat hemispherical shape whose height direction is shorter than the diameter direction. The method according to claim 1,
Wherein an existence density of the printed dots on the back surface of the base sheet is 10 / mm ² to 2500 / mm ² . The method according to claim 1,
Wherein the main component of the printed dot is an acrylic type, urethane type or an acrylic urethane type resin. The method according to claim 1,
Wherein the substrate sheet has a base layer and another functional layer arranged on the back surface of the base layer, and the printing dot is formed on the back surface of the functional layer. 8. The method of claim 7,
Wherein the functional layer is an antistatic layer. The method according to claim 1,
Further comprising a light-diffusing layer laminated on the surface side of the substrate sheet, wherein the light-diffusing layer has a light-diffusing agent and a binder therefor. 10. The method of claim 9,
Wherein an average height of the printed dots is larger than an average particle diameter of the light diffusing agent. 10. The method of claim 9,
Wherein the average diameter of the printed dots is at least 2 times and not more than 20 times the average particle diameter of the light diffusing agent. An optical sheet according to claim 1; And
A light guide plate arranged on the back side of the optical sheet;
And a backlight unit which is disposed on the backlight unit. 13. The method of claim 12,
Wherein the light guide plate has a plurality of concave troughs arranged so as to be substantially parallel to the surface of the backlight unit. 14. The method of claim 13,
Wherein an average diameter of the printed dots is equal to or greater than an average width of the recessed treads. The method according to claim 1,
Wherein the light guide sheet is an edge light type backlight unit for a backlight unit that emits light beams incident from an end face to a surface. 16. The method of claim 15,
Wherein the printed dot contains a white pigment. 16. The method of claim 15,
Wherein the substrate sheet has a wave-like fine modulation structure on the surface thereof. An edge light type backlight unit comprising the optical sheet according to claim 15.

Images